Peptides that become prevalent in tumor vessels or tumor cells by specifically binding to surface molecules of tumors are usually used as tumor targeting reagents.
Tumor-targeting peptides have an important value when applied to diagnosis of tumor and targeted treatment. On the one hand, tumor-targeting peptides coupled with imaging molecules could be applied to tumor imaging; on the other hand, tumor-targeting peptides coupled with anti-tumor drugs could be used in tumor-targeted treatment. For example, Professor Errki, an academician of the National Academy of Science, reported a tumor-targeting peptide containing RGD motif, which binds to integrin αv of angiogenic blood vessels in tumor. Based on Professor Errki's study, many tumor-targeting peptides containing this RGD motif have emerged in the clinical research and some of the peptides have gotten satisfactory results. One of the tumor-targeting peptide containing RGD motif is called “Cliengtide.” “Cliengtide” has shown good efficacy on glioma during Phase II clinical trial and has entered Phase III clinical trial stage.
Based on the targeting and penetrating features of tumor-targeting peptides, Professor Errki divided them into 4 types: the first type can target tumor vessels; the second type can target tumor cells; the third type can target both tumor vessels and tumor cells; the fourth can target and penetrate both tumor vessels and tumor cells by binding to tumor vessels and tumor cells, and entering the tumor's cytoplasm through tumor cell membrane. Professor Errki considered the fourth type such as the iRGD peptide as the most ideal tumor-targeting peptides.